This proposal addresses the continued development of a rapid, inexpensive assay to screen nasopharyngeal secretions for influenza A. The assay utilizes a novel biosensor, with molecular recognition/binding as the detection element and a proprietary, integrated optic interferometer as the transducer. The unique design of the interferometer allows direct quantification of very low concentrations of specific biomolecules in a fluid sample. The approach relies on the detection of small refractive index changes at the surface of the interferometer. When receptor molecules are immobilized on the interferometer surface, the subsequent binding of specific ligands results in a pronounced refractive index change. An assay based on this approach has a number of key advantages: 1) it is rapid (less than 5 minutes), 2) it is sensitive (less than 104 pfu/milliliter), 3) it is simple (no labeling or tagging) and 4) it is low cost (less than cost, no expensive analytic instrumentation). The biosensor can be packaged as a hand-held device, suitable for out-of-lab use. Moreover, the technology offers the potential of simultaneously testing for several respiratory infections (e.g.; influenza A, influenza B, RVS, parainfluenza) in a single assay. Phase I experiments have demonstrated concept feasibility, and it is now proposed to proceed to Phase II development and testing of a clinical prototype. PROPOSED COMMERCIAL APPLICATION: Influenza is unique in its ability to cause annual epidemics of respiratory illness and ranks among the leading causes of excess mortality in the United States. The proposed assay would provide a rapid, low-cost tool for detecting institutional outbreaks of influenza A (which amantadine or rimantadine might be used to control) and for making differential diagnoses (eg; influenza vs. RSV in the young and old, influenza vs. hantavirus infection at all ages).